High pressure discharge lamp

Abstract

A high pressure discharge lamp includes an outer tubular bulb whose inner space is exhausted to a vacuum; an arc tube contained in the outer tubular bulb; and a voltage reducing switching element for reducing a voltage applied to the arc tube. The voltage reducing switching element includes a heat sensitive switching element and a starting-voltage reducing element which are connected in series. During a period in which the heat sensitive switching element has a predetermined temperature or higher, the heat sensitive switching element is closed to electrically connect the arc tube and the voltage reducing switching element in parallel, so that the starting-voltage reducing element is operated. During a period in which the heat sensitive switching element has a temperature lower than the predetermined temperature, the heat sensitive switching element is opened so that the starting-voltage reducing element is not operated.

1. A high pressure discharge lamp comprising:
 an outer tubular bulb whose inner space is exhausted to a vacuum; 
 an arc tube contained in said outer tubular bulb; and 
 a voltage reducing switching element for reducing a voltage applied to said arc tube, said voltage reducing switching element comprising a heat sensitive switching element and a starting-voltage reducing element which are connected in series, 
 wherein during a period in which said heat sensitive switching element has a predetermined temperature or higher, said heat sensitive switching element is closed to electrically connect said arc tube and said voltage reducing switching element in parallel, so that said starting-voltage reducing element is operated, and 
 during a period in which said heat sensitive switching element has a temperature lower than the predetermined temperature, said heat sensitive switching element is opened so that said starting-voltage reducing element is not operated. 
 
   
   
     2. The high pressure discharge lamp in accordance with  claim 1 , wherein said arc tube is fixed in said outer tubular bulb by a first lead and a second lead which supply the voltage applied to said arc tube, and said voltage reducing switching element is fixed to at least one of said first lead and said second lead. 
   
   
     3. The high pressure discharge lamp in accordance with  claim 1 , wherein said heat sensitive switching element comprises a bimetal element. 
   
   
     4. The high pressure discharge lamp in accordance with  claim 1 , wherein said heat sensitive switching element comprises a temperature sensitive lead switch that is turned on at a temperature equal to or higher than said predetermined temperature. 
   
   
     5. The high pressure discharge lamp in accordance with  claim 1 , wherein said starting-voltage reducing element comprises a capacitor. 
   
   
     6. The high pressure discharge lamp in accordance with  claim 1 , wherein said starting-voltage reducing element comprises a surge absorber element.